66 coupe - need help w/ electrical problem

[Bill F.]

1. There are no blown fuses.
2. There is no visible damage to the wiring under the dash.
3. Pulled the cover off the regulator and there is no visible scorching or burnt smell inside.
4. Removed the distributor shielding and there is no apparent damage to the wires to the coil or the distributor.
5.
6. Decided to try cranking it. The car cranked and runs fine. Harness did not get hot although I did not run it for more than 5 minutes (and the heater was off).

alternator battery terminal.
b. Re-started and ran well several times while checking.


that before.

[Ronald L.]

Re: 66 coupe - need help w/ electrical problem

An alternator shop should be able to tell you what happened but it is clear something is probably wrong with that alternator, never seen them spark, if they did and you had a leaking carb??? Deadly combination.

Was that the standard (55 amp)with air? or was it the 37Amp Alt?

The 55 is putting out more juice but that should be regulated on demand so between the pieces replaced something is amiss. Since you mention the heater, that is fused, and given that you noted the Bat gauge did not move implies the regulator is stabilizing the current according to need.

The regulator theoretically should not permit an over load such that you smoked the wire harness too.

At a top level I'd say you got a bad rebuild on that alternator.

[Bill F.]

Re: 66 coupe - need help w/ electrical problem

I agree on both counts on the alternator - when I noted the sparking I shut it down.

55 amp is correct for cars w/ air conditioning.

I'm curious though - what would have shut the car off (glad it did or the wiring probably would have been on fire by the time I got home), and why does it now crank and run fine? Are there fusible links in the harness, but if there were and they broke it wouldn't re-start, right?

[Ronald L.]

Re: 66 coupe - need help w/ electrical problem

Was the battery essentially dead when the car shut off and you got a tow?

If yes, then that trip was on the battery...ask me how I know>>>

A blown diode - you never know when they blow and the car runs on the battery for a while then, dies suddenly. I want to say that on a friends battery I used half of it getting back home (about 15 miles).

It may be two things, you have this mis-wired and it blew the alternator and fried the wiring, or the alternator popped when first started or within a few minutes. If it is just the alternator I am surprised you fried the wiring which leads me to a wrong connection. It might help to post a picture of your connections and the burnt wiring. Regardless the alternator should be diagnosed by a shop that specializes in rebuilding these.

[Bill F.]

Re: 66 coupe - need help w/ electrical problem

The wiring harness doesn't really leave a lot of options - I put wires back to the same terminals on the alternator (2 wires and a plug) and regulator (4 wire plug and a ground) that they were on when I removed the old parts. It has been wired this way since I bought the car w/ no problems.

I did not check the battery while on the side of the road - just very glad when the harness stopped smoking w/o further drama! It had been on the tender for a week before I started checking this weekend, so hard to say.

The gauge had not registered any discharge prior to the shut off.

[Randy S.]

Re: 66 coupe - need help w/ electrical problem

[quote=Bill Flammer (23767);536341]I agree on both counts on the alternator - when I noted the sparking I shut it down.

55 amp is correct for cars w/ air conditioning.

Bill,

For 66 small block with C60 (air cond) should be 1100750 61 amp alternator

Randy

[Bill F.]

Re: 66 coupe - need help w/ electrical problem

The Corvette vender that I purchased the alternator from offered only the 37 amp standard and the 55 amp, represented for a/c cars. Do you think the difference between the 55 amp and the 61 amp could have caused the problem.

[Ronald L.]

Re: 66 coupe - need help w/ electrical problem

Should not have, you were not running the air, might have been a load problem on the 37 amp. I think you got a bad part. But it would be good to see pics of what you really have.

[Domenic T.]

Re: 66 coupe - need help w/ electrical problem

Bill,
I just converted my altinators to higher amp out put, simply by installation only. All the parts look the same but the windings are different in size and the diods may have a different rating but I doubt it.

It sounds like othe insulated diod pack could have grounded.
That will cause the B+ (battery charge) terminal to burn thru the regulator.

They insulate the pac around the screw holes and pac to altinator.

That or the brush that comes from the insulated pack is grounding if you saw sparks in the altinator, although it is possible for a regulator to cause a problem that could cause the altinator sparks if it grounds the charge lead.

Here is a pic of one apart and the insulated diod pack of 3 is out along with the screws and insulators.

I think you will have to take the altinator apart and see if you can find a fault. If none then the regulator or other grounded wire may be the culprit. Check the horn relay also, it is not fuesed either.

Not much help and the rebuilder is not going to stand for you to touch his work and the place where you bought the new regulator will also want to slide.
Disconnect the wires from the alt and check the B+ for ground. If it is not grounded start the car and touch the field with 12 volts ( you can do this with a test light hooked to 12 volts) and see if you have out put. It will be way up there.
That's a starting point. GOOD LUCK

DOM

[Bill F.]

Re: 66 coupe - need help w/ electrical problem

DOM,
One of the tests I ran was to disconnect the plug at the regulator, attach a volt meter to the battery, crank the car and put a jump wire between the F and #3 terminals in the regulator plug. Voltage at the battery went up like a rocket - 17, 18 volts and I pulled the jumper. I understand that the jumper should reflect some increase in voltage @ the battery, but not that fast. Any thoughts on that?

I'm going to strip what's left of the harness cover off the burned section and see if I can find a damage section of wire, then using the wiring chart try to chase that back to the source. The wires I can see look fine, and the harness did not get hot (felt several places) when the car was running this weekend.

Thanks, Bill

[Domenic T.]

Re: 66 coupe - need help w/ electrical problem

Bill,
just got back and read your post.

Yes that is what a good altinator should do. If you would have disconnected the battery and tested it you would see close to 100 volts DC.
These alternators are the best and take a lot of abuse contrary to what some might say.
I took one and hooked it to a briggs & stratton and lit the place up while running a 1/2 in drill.
The common test (unothorized)to see if your charging system was working was to take the negative cable off while the engine was running.
If the engine did not stop things were good, if it did things were not so good. Most ran the engine at about 1200 RPM to do this test, the pulley diameter was a factor on some HP engines.
I have a production portable welder that uses these altinators (1)and it burns the rods at 90 amps.

DOM

[John H.]

Re: 66 coupe - need help w/ electrical problem

Are there fusible links in the harness, but if there were and they broke it wouldn't re-start, right?

Bill -

Fusible links in the charging circuit didn't appear until 1967; prior to that, those circuits were completely unprotected in the event of a short.

[Bill F.]

Re: 66 coupe - need help w/ electrical problem

Anyone know the correct gauge fusible link to add? Would it go in the main feed (red wire) to the starter solenoid? Thanks

[John H.]

Re: 66 coupe - need help w/ electrical problem

Anyone know the correct gauge fusible link to add? Would it go in the main feed (red wire) to the starter solenoid? Thanks

Bill -

Your main power feed from the battery cable stud on the starter solenoid is a 10-ga. red wire; the correct fusible link for that application would be 14-gauge. Any good auto parts store will have it, with the large ring terminal already on it.

[Bill F.]

Re: 66 coupe - need help w/ electrical problem

Thanks John